The functional specifications of a battery used in self-contained self-powered portable devices (SSPD), such as radio frequency identification (RF-ID) tags and smart cards, include a nominal cell voltage of 3 volts, high energy density and specific energy, which generally necessitates the use of a primary (non-rechargeable) lithium battery. However, such a battery must also be extremely flexible and small, generally not more than about 0.3 millimeter in thickness and a few square centimeters in surface area. In addition to RF-ID tags, it is believed that batteries having the above characteristics would also be well suited for other SSPD applications in the mobile electronics and communications industries.
While small flexible batteries are generally known in the art, as evidenced by U.S. Pat. No. 4,092,464 to Dey et al., their performance, manufacturability, cost-efficiency and/or durability are generally inadequate for use in SSPDs. In particular, the present technology of lithium canisters, or button cells, does not provide the flexibility demanded by SSPD applications, and is severely constrained in the thickness of the cells that can be reliably and repeatably formed in mass production. Reduction in cell thickness is often limited by the thickness of the battery buttons, which generally is greater than about 50 micrometers, such that the battery buttons constitute a sizable portion of the overall battery thickness.
Accordingly, what is needed is a light-weight, thin and flexible primary battery which can be readily and reliably manufactured to be suitable for powering an SSPD.